FIELD OF THE INVENTION
The invention pertains to a windshield wiper system, in particular for passenger vehicles, with a wiper arm having a pivot drive and comprising at least two telescopically shiftable members, with a wiper blade pivotally mounted at a free end of the shiftable wiper arm member and guidable transversely across substantially the entire surface of the windshield, with a cable line having two cable lengths between a cable pulley associated with the wiper blade and a base part effecting the pivoting of the wiper blade, with a second cable drive for extending the extendable wiper arm member, the drawing-in of which is effected by the first cable line, and with a cable storage for receiving and issuing the section of each cable length of the first cable line corresponding to the wiper arm length difference.
Such a windshield wiper system is described, for instance, in AT-PS 392 942. The sections of the two cable lengths corresponding to the length of the wiper arm are wound onto two cable pulleys which are driven in contrary directions and which are disposed in the pivot bearing either next to one another or above one another. The extension is effected by means of a helical spring acting on the shiftable wiper arm instead of which a second cable line, which is not discussed in detail, can be provided.
The bearing axes of the two cable pulleys do not change their position during the oscillation and therefore form the above-mentioned base part, relatively to which the wiper arm is pivoted and which causes the rotation of the pulley, which attains an at least nearly parallel movement of the wiper blade. This leads particularly to constructional problems in terms of dimensioning of the windshield wiper and, in particular, of the wiper arm, which should or must have a cross-sectional width as little view-obstructive as possible and, if a tension spring surrounding the wiper arm is provided, in terms of the continuous spring action and in that the spring is itself surrounded by a bellows. Since the wiper blade is to wipe the full surface of the windshield, the shape of the windshield determines the accuracy of the parallel guide. In the case of a rectangular windshield, it is exact; due to the fact, however, that most windshields have oblique edges, i.e. they are trapezoid, the wiper blade is subject to a slight rotation by a few degrees during the wiping oscillation.
The invention is based on the object to provide dimensions, in a windshield wiper system of the above-mentioned kind, in particular the width and the height (perpendicular to the windshield) of the wiper arm and its pivot bearing as small as possible.
This is attained, in accordance with the invention, in that the second cable line comprises a push-out cable which is guided from a driven first cable pulley mounted in the pivot bearing of the wiper arm, via a second cable pulley disposed at a constant distance from the first cable pulley on the pivoted wiper arm member, to the extendable wiper arm member, and a draw-in cable which is guided back from the extendable wiper arm member to the driven first cable pulley, whereby the first cable line is formed in one of the two cables of the second cable line.
Guiding the second cable line via two fixedly spaced-apart cable pulleys reduces the width and the height of the wiper arm, because the two cables of the second cable line can be guided inside the wiper arm as well, and it reduces the height of the pivot bearing, because only a single driven cable pulley must be accommodated.
In a first preferred embodiment, the cable storage for the first cable line includes a segment of the periphery of the driven first cable pulley. In spite of the rotation of the driven cable pulley about the pivot axis, the orientation of the wiper blade is maintained, since both cable lengths are drawn-in and released by the same amount.
Guiding the two cable lengths of the first cable line to the cable-storing peripheral segment is, in principle, possible in various ways, whereby at least one cable length can possibly also be guided about a guide roller, in order to attain the same draw-in direction and release direction for both cable lengths. A structurally simple embodiment, however, provides for a common feed of the two cable lengths of the first cable line into the cable-storing peripheral segment of the driven cable pulley.
For the purpose of maintaining the diameter of the driven first pulley as small as possible, the cable-storing peripheral segment extends about a largest possible arc. The angle of rotation of the cable pulley is thus larger than the pivot angle of the wiper arm between its two reversal positions. An additional drive for the cable pulley is obviated in that a transmission gearing is formed between the pivot drive of the wiper arm and the driven first cable pulley of the second cable line disposed in the pivot bearing of the wiper arm.
Starting out from a center position of the wiper arm, in which it has the shortest length, the wiper arm is extended up to the reversal position and again retracted to the center position. The same movements take place in pivoting in the other direction. The cable pulley is controlled via the transmission gearing in this manner, whereby, preferably, there is provided, a toothed rack which is guided in the pivoted wiper arm member, which meshes with a pinion of the cable pulley, and which is moved along a chord-like guide track in the pivot bearing. Accordingly, any pivoting of the wiper arm from the center position to the reversal position and back into the center position, effects a rotation of the driven first cable pulley in both directions.
In a preferred embodiment it is provided that the two cable lengths of the first cable line are guided through a device for variable loop formation, which comprises guide rollers which are movable relative to one another and which effect the pivoting of the wiper blade. The device for variable loop formation preferably also forms the basic part, the position of which is thus independent of the driven first pulley, which, again, has an advantageous effect on the dimensions of the windshield wiper system. The cable length changes effected in the device for loop formation can be adapted to the pivot angle of the wiper blade if a reduction gearing is provided between the pulley and the pivot bearing. Additionally, it can equalize great cable length changes which is particularly advantageous when the device for variable loop formation includes two first guide rollers associated with the pivot bearing and two second guide rollers disposed at the pivoted wiper arm member, so that a hoist-like cable deflection is provided through which the external forces and torques acting on the wiper blade are transferred in a reduced fashion onto the parts of the transmission gearing between the driven cable pulley of the second cable line and the pivot drive of the wiper arm.
In a first embodiment, the two first guide rollers are disposed on the pivot bearing at an angle relative to the pivot axis which is, in particular, greater than the pivot angle of the wiper arm. An arc-shaped sliding guide for the cable lengths of the first cable line may be provided between the two first guide rollers, so that the loop formation and loop variation changes the two cable lengths of the first cable line by the same amount in correspondence with the pivot angle of the wiper arm. Several first guide rollers may be provided along the arc for the purpose of reducing friction, whereby the difference between the partial lengths of the arc between the two first guide rollers and the respective pivot lengths can be neglected. The error becomes smaller, the more closely the first guide rollers are disposed next to one another.
In a second embodiment, the two first guide rollers are also disposed on the pivoted wiper arm member, but shiftable in length, and a control surface is provided at the pivot bearing whose orientation determines the shifting of the guide roller pair. A control pin connected with the guide roller carrier senses the control surface during the pivoting, which control surface is preferably formed in a plane, resulting in a steady pivoting of the wiper blade. At least segments of the control surface, however, may also be curved if an "uneven parallel guide" is required.
A further preferred embodiment provides for the two cable lines to consist of a single cable, which--as the push-out cable--is guided from the fixed point of the first cable end at the extendable wiper arm member, via the second cable pulley, to the driven first cable pulley, and--as the draw-in cable comprising the two cable lengths of the first cable line--from the driven first cable pulley, via a first guide roller and a second guide roller, to the pulley at the extendable wiper arm member, and via a further first guide roller and a further second guide roller back to the driven first cable pulley, at which the fixed point for the second cable end is disposed in the entrance region for the push-out cable leading from the second cable pulley to the first cable pulley. Depending on the embodiment, the cable can be guided about additional first and/or second guide rollers.
The invention will now be described in more detail by means of the figures of the enclosed drawings: